Tunneling Ground Classification: RMR_Bieniawski
Rock mass classification systems for tunnel design — RMR (Bieniawski 1989), Q-system (Barton 1974), GSI (Hoek 2002), NATM classes, and squeezing potential (Hoek & Marinos 2000) with support requirements, TBM performance parameters, and convergence estimates
| classification system | rock class | GSI max (dimensionless) | GSI min (dimensionless) | Q max (dimensionless) | Q min (dimensionless) | RMR max (dimensionless) | RMR min (dimensionless) | TBM penetration rate m per hr (m/hr) | TBM utilization pct (%) | advance rate m per day (m/day) | bolt length m (m) | bolt spacing m (m) | class number | convergence pct (%) | cutter wear index | max unsupported span m (m) | notes | overbreak pct (%) | recommended support | rock class variant | shotcrete thickness mm (mm) | specific energy MJ per m3 | stand up time hr (hr) |
|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|---|
| RMR_Bieniawski | III_fair__shotcrete | 55 | 35 | 10 | 1 | 60 | 41 | 1.5 | 40 | 20 | 4 | 2 | 3 | 0.5 | 0.6 | 8 | Class III lower bound: 50 mm shotcrete plus systematic bolts 4 m at 2 m spacing. | 4 | shotcrete | III_fair__shotcrete | 50 | 55 | 10 |
| RMR_Bieniawski | III_fair__systematic_bolts | 55 | 35 | 10 | 1 | 60 | 41 | 1.5 | 40 | 20 | 4 | 1.5 | 3 | 0.5 | 0.6 | 8 | Class III: Fair rock. Systematic bolts 4 m long spaced 1.5-2.0 m in crown and walls with wire mesh. Shotcrete 50-100 mm in crown and sides. RMR=41-60. | 4 | systematic_bolts | III_fair__systematic_bolts | 100 | 55 | 10 |
| RMR_Bieniawski | II_good__spot_bolts | 75 | 55 | 40 | 10 | 80 | 61 | 2 | 45 | 30 | 3 | 2.5 | 2 | 0.2 | 0.3 | 15 | Class II: Good rock. Locally bolts in crown 3 m long spaced 2.5 m with occasional wire mesh. Shotcrete 50 mm in crown where required. RMR=61-80. | 2 | spot_bolts | II_good__spot_bolts | 50 | 40 | 100 |
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